This invention relates to nickel-base alloys which can be hot worked without cracking.
It is known that nickel-base alloys containing beryllium at levels of about 2 weight percent are precipitation hardenable. The annealed condition of such alloys is obtained by heating to a temperature of 1800.degree.-2000.degree.F. followed by water quenching. In this condition, the alloy is soft (R/C-10), ductile, and malleable and readily fabricated, formed, or machined. The hardened condition is obtained by tempering the annealed structure at temperatures between 800.degree. and 1000.degree.F.; particularly, at 925.degree.-950.degree.F. for 11/2 hours. In this condition, the annealed structure is not only hardened, but has good strength and ductility. The strength of this alloy can be further increased by the addition of titanium without adversely affecting the ductility of the alloy in the hardened state. Such a nickel-base alloy is, for example, illustrated in U.S. Pat. No. 3,287,110.
Industrial needs, however, require the production of wide sheets of such nickel-base alloys starting from cast billets having a cross-section in excess of 1 foot square and weighing 1,000 pounds. Utilizing the known nickel-beryllium-titanium alloys to form such sheets using standard steel industry hot rolling practice has resulted in cracks developing in the castings during such working. Such alloys are somewhat hot short which, it is believed, might be due in some measure to interstitial impurities in the metal, in particular, sulfur. Such billets because of this cracking are unsuitable for hot working and, in fact, it has been noted that their cold workability and resistance to grain growth at elevated temperatures are not satisfactory.